Full T/O power on take off!
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OS,
I am VERY clear on the implications of TOGA power being (mis)used post a V1 cut especially with low weights and thus low Vmca. You hit TOGA,the BRT's churn out max un-derated thrust @ 115k a piece! And then the issues of low flight regime controllibility etc etc(I was personally involved with the removal of some very 'set' ideas WRT usage of TOGA post V1 cut).
That's a taken.
So's the fact that one would be have to be very circumscept in its use at especially low weights and as such constitutes additional briefing(at the very least) IF and WHEN TOGA would be used post EF on T/O roll in very low weights...ie obstacles,windshear etc etc.
That said,I completely agree with John.T in that a derate is tantamount to an engine change with a lower max power.Therefore,firewalling the engines ON TAKE OFF ROLL,having used assumed temp+derate would only give me max derate power...
Which gets me back to my original question ..
PS-Just to keep u in perspective..errm,I am not a '7-8 year RHS flown FO with little understanding of the t7'. Am just doing some brainstorming here.And happens to be some valuable brainstorming,by what I see...
Just so we're on the same page please. No offence here..
Thanks all
I am VERY clear on the implications of TOGA power being (mis)used post a V1 cut especially with low weights and thus low Vmca. You hit TOGA,the BRT's churn out max un-derated thrust @ 115k a piece! And then the issues of low flight regime controllibility etc etc(I was personally involved with the removal of some very 'set' ideas WRT usage of TOGA post V1 cut).
That's a taken.
So's the fact that one would be have to be very circumscept in its use at especially low weights and as such constitutes additional briefing(at the very least) IF and WHEN TOGA would be used post EF on T/O roll in very low weights...ie obstacles,windshear etc etc.
That said,I completely agree with John.T in that a derate is tantamount to an engine change with a lower max power.Therefore,firewalling the engines ON TAKE OFF ROLL,having used assumed temp+derate would only give me max derate power...
Which gets me back to my original question ..
PS-Just to keep u in perspective..errm,I am not a '7-8 year RHS flown FO with little understanding of the t7'. Am just doing some brainstorming here.And happens to be some valuable brainstorming,by what I see...
Just so we're on the same page please. No offence here..
Thanks all
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Thrust is derated by the use of program plugs on the EEC's
the pilot does not have access to rated thrust.
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In tech training right now on the B77f, asked the instructor these direct questions. Have access to the origional books (co ones used). Guess the old saying is true... Those who can do, those who can't teach.
Taking in mind the MD-11 fadec bar, I could not understand how an aircraft could be manufactured W/O access to full thrust/exceedence if needed. I learn more here. THX
Taking in mind the MD-11 fadec bar, I could not understand how an aircraft could be manufactured W/O access to full thrust/exceedence if needed. I learn more here. THX
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That said,I completely agree with John.T in that a derate is tantamount to an engine change with a lower max power.Therefore,firewalling the engines ON TAKE OFF ROLL,having used assumed temp+derate would only give me max derate power...
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1) Why touch the TOGA button after engine failure? The calculated derate covers the obstacle clearance. It is just (sometimes) a long sit to flap retraction altitude.
I specifically brief the use of derate and the dangers involved as we not do it on a daily basis (empty/postitioning flights).
2) I always wondered wy the assumed temp will not go beyond 60 degrees C (in my company, B737). Is there as special reason why not to allow 100 degrees??? It gives the benefit of not to worry about V2min etc...
I specifically brief the use of derate and the dangers involved as we not do it on a daily basis (empty/postitioning flights).
2) I always wondered wy the assumed temp will not go beyond 60 degrees C (in my company, B737). Is there as special reason why not to allow 100 degrees??? It gives the benefit of not to worry about V2min etc...
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Is there as special reason why not to allow 100 degrees???
In some cases, Airbus have obtained approval to operate with Flex thrust reductions of -40%, in these cases you will see assumed temperatures in the 70's.
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From what I understand as studied and been told by experts. For the GE90-115b, my operator has a hard EEC program plug derate to 110k, does not matter how many times you click TOGA you get 110k.
Your company restricts max thrust under contract with the engine manufacturer (in some cases for overhaul contracts) or on their own to the thrust allowed by the hard wired program plug on the eec. My previous post to engine out was false. All of your limiting performance data is based on this.
Full rated thrust as a pilot understands is the limited thrust by FADEC, you will get no more as the GE-90-115 is capable of 127k as I hear in the test cell. Rudder authority in an engine out situation would not compensate at 127k and engine wear (overhaul contracts) are based on the hard de-rate setting (more hrs on wing in between)
Your company restricts max thrust under contract with the engine manufacturer (in some cases for overhaul contracts) or on their own to the thrust allowed by the hard wired program plug on the eec. My previous post to engine out was false. All of your limiting performance data is based on this.
Full rated thrust as a pilot understands is the limited thrust by FADEC, you will get no more as the GE-90-115 is capable of 127k as I hear in the test cell. Rudder authority in an engine out situation would not compensate at 127k and engine wear (overhaul contracts) are based on the hard de-rate setting (more hrs on wing in between)
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Not the case with my company.
I have a choice of three (fixed value) derates to choose from. And then I can do an assumed temperature on either. Thus the question..
All these derates are selectable from the FMC and the Vspeeds are calculated accordingly,after the derate value has been selected and the assumed temperature plugged it.
I have a choice of three (fixed value) derates to choose from. And then I can do an assumed temperature on either. Thus the question..
All these derates are selectable from the FMC and the Vspeeds are calculated accordingly,after the derate value has been selected and the assumed temperature plugged it.
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KOW are you speaking of max flex (from what I understand on the -115 is limited to 20% less than max derated), TOGA is 10% less than max de-rated then 2nd click TOGA that brings you up to max de-rated thrust.
I am talking GE here and do not know but expect by example it would be the same for the -94 etc.
I am talking GE here and do not know but expect by example it would be the same for the -94 etc.
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I don't fly a boeing, but E170/E190's.
The posters question seems pretty reasonable. We have TO-1, TO-2 and TO-3, all of which we can flex.
Most of the guys in work are surprised to learn that if we use TO-3 with a flex, it does not matter how hard or how far we push the thrust levers, we are not going to get any more thrust than TO-3 no flex, with 2 exceptions.
1. Windshear will give WSHR thrust.
2. Engine failure will give us Reserve power, but only TO-3 reserve.
If we have completley messed up our performance, and the end of the runway, or an obstacle is rapidly approaching and we wan't to get away from TO-3 flex to TO-1, then some very quick FMS programming would be required.
The posters question seems pretty reasonable. We have TO-1, TO-2 and TO-3, all of which we can flex.
Most of the guys in work are surprised to learn that if we use TO-3 with a flex, it does not matter how hard or how far we push the thrust levers, we are not going to get any more thrust than TO-3 no flex, with 2 exceptions.
1. Windshear will give WSHR thrust.
2. Engine failure will give us Reserve power, but only TO-3 reserve.
If we have completley messed up our performance, and the end of the runway, or an obstacle is rapidly approaching and we wan't to get away from TO-3 flex to TO-1, then some very quick FMS programming would be required.
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Read all throught this and some interesting points made, claims, counterclaims etc. The only thing that does seem clear, is that there are many, many who think they know but actually don't.
Just wondered, why - if using de-rate you would ever want full flat rated power anyway.
Apart from the issues with vmcg, all your obstacle clearance for engine failure is covered by your weight tables anyway. So providing you RTOW is derived from the derate/assumed method you have all the power you need even with an engine failure at T/O.
My understanding is the most engine failures at T/O are at full stress, so to increase the EGT on your remaining engine (when the power you have will already suffice) puts an increased risk that you will lose that engine too?
Just wondered, why - if using de-rate you would ever want full flat rated power anyway.
Apart from the issues with vmcg, all your obstacle clearance for engine failure is covered by your weight tables anyway. So providing you RTOW is derived from the derate/assumed method you have all the power you need even with an engine failure at T/O.
My understanding is the most engine failures at T/O are at full stress, so to increase the EGT on your remaining engine (when the power you have will already suffice) puts an increased risk that you will lose that engine too?
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@ORJ
There is no guarantee that in a real-world failure scenario that you "have all the power you need even with an engine failure at T/O". The certification rules for determining single engine failure performance are specific, and not all-encompassing; there are failure scenarios that will result in losing more performance that is assumed.
So while there are very good reasons to leave the thrust where it is supposed to be - VMC not the least of those - someday someone will wish they had the full rated thrust, not the available derated max.
One example, is any failure which causes the failed engine to fail to windmill. The additional drag for a locked fan is considerable.
There is no guarantee that in a real-world failure scenario that you "have all the power you need even with an engine failure at T/O". The certification rules for determining single engine failure performance are specific, and not all-encompassing; there are failure scenarios that will result in losing more performance that is assumed.
So while there are very good reasons to leave the thrust where it is supposed to be - VMC not the least of those - someday someone will wish they had the full rated thrust, not the available derated max.
One example, is any failure which causes the failed engine to fail to windmill. The additional drag for a locked fan is considerable.
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Say you derate.
When you go land a bit later somewhere else, and make a go-around, you might need full go-around trust due to weight and obstacles. So full go around trust is available here by pushing TOGA twice. This trust can not be a function of the derate you set at your departure airport, right?
When you go land a bit later somewhere else, and make a go-around, you might need full go-around trust due to weight and obstacles. So full go around trust is available here by pushing TOGA twice. This trust can not be a function of the derate you set at your departure airport, right?
Care to elaborate ... ?
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Ok. You take off at a long runway. no obstacles. I speak for the B737. You derate, and probaly use ATM for your take off. Your engine rating is now 22k.
Your destination is 30 min further on, rwy with on the other end obstacles. In the event of a go-around here, you do not want to rely on a 22k derated engine, but full go around thrust. Especially if you would loose an engine. So TOGA (twice) can give you 26k..
Your destination is 30 min further on, rwy with on the other end obstacles. In the event of a go-around here, you do not want to rely on a 22k derated engine, but full go around thrust. Especially if you would loose an engine. So TOGA (twice) can give you 26k..
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before you depart should you not check your LDA/weight restriction at planned airfield and alternates for a) most favourable and b) most likely (due WX forecast etc.) and then ALSO check your go-around gradient limiting weights?
If these are lower than your current RTOW, you need to reduce it further - de-rate, assumed or normal take-off?
that's what I thought.
If these are lower than your current RTOW, you need to reduce it further - de-rate, assumed or normal take-off?
that's what I thought.
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No, it goes full thrust on 2nd Toga. Also just after T/O. That is exactly why you should not do it, but advance maximum to the green N1 indicator, which is your derated trust. (Not the double derate with ATM included). Pushing TOGA moves the N1 indicators up to full trust.